Automatic brake for gyroscopic instruments



April 7, 1942. CARTER 2,278,913

AUTOMATIC BRAKE FOR GYROSGOPIC' INSTRUMENTS Filed Dec. 20, 1939 7aVacuum INVENTOR BY ,flm WAT'TORNEY.

scope will strike limit stops or Patented Apr. 7, 1942 UNITEDINSTRUMENTS Leslie F.

Gyroscope Company, corporation of New Y Carter, Leonia, N. 3.,

line, Brooklyn,

assignor to Sperry N. K, a

ork

Application December 2c, 1939, Serial No. aroma (on. ti e) 7 Claims.

This invention relates togyroscopic artificial horizons orgyro-verticals, especially adapted for use on aircraft. vAs at presentdesigned, such instruments are well suited for ordinary flight, but arenot adapted for use during the performance of aerial acrobatics, atwhich time the gyrohave its gimbals which usually causes upsetting ofthe gyro. The present practice is to provide such apparatus, when usedon a plane which may perform acrobatics, with a caging or locking deviceso that the gyroscope may be locked in its gimbals during such stuntsand released again when normal flight is resumed. This system, however,requires a rather complex cagcrossed, either of ing device to centralizethe gyroscope about both horizontal axes and, in addition, is notentirely satisfactory since the gyro may be released in an inclinedposition and, owing to its slow precession, will require some minutes toresume the vertical position of its spin axis. Especially is this sowhere the rate of erection is made small, as disclosed in my priorPatent No. 2,219,295, for Pneumatic erection device for gyroscopes,.flled March 18, 1939.

According to my present to overcome the difiiculties invention, Ipropose by an automatically .operated brake operating directly on thegyro rotor and automatically brought into operation by the simpleexpedient of shutting off the air supply to the gyroscope. By thismeans, the

"rotor is quickly brought to rest and hence the gyroscopic forcesdestroyed which cause violent striking of the stops and strains on thepivots during acrobatics. By the same means I prefer also to lower thecenter of gravity at the time the brake is applied; so that the devicebecomes pendulous enough to remain in a substantially vertical positionwhen inoperative as a gyroscope. Therefore, when the acrobatics areconcluded, all the aviator need do is to open the air valve on thehorizon, which will cause release of the brake and start the rotorspinning; The gyroscope will therefore be quickly erected, since it isnear the vertical position at the time due to its pendulosity.

Referring to the drawing, showing the preferred form my. invention mayassume,

Fig. 1 is a side elevation, partly in section, of a gyroscopicartificial horizon with my automatic brake attached thereto.

Fig. 2 is a vertical section, on an enlarged scale, through the gyrocasing taken substantially on line 2-2 of Fig. 1. i

I- have shown my invention as applied gyroscopic artificial horizon suchas employed on aircraft. Such instrument is usually mounted within asealed casing I having a transparent front window 2 through which ahorizon bar 3 actuated from the gyroscope is visible. Such 'gyroscopesare usually air drivenfrom a suitable air pump which maintains an airsupply either above or below atmospheric pressure. In the form of theinvention illustrated, air is continu= ously exhausted from the interiorof the casing B, through a valve 4 and pipe coupling 5 connected to avacuum pump or Venturi tube (not shown). Air at atmospheric pressure isadmitted through a screened opening 6 in the rear of the case, the airpassing in through one of the 'trunnionsi, 1' of the gimbal ring 8,which is made hollow for the purpose. channel 9 in said gimbal andthrough one of the minor trunnion axes HI, which is made hollowfor thepurpose and which supports the rotor bearing casing H within the gimbalring 8. The air then passes through a channel l2 in the casing andemerges through one or more nozzles (not shown) for spinning the rotor13. The used air passes downwardly through hollow extension I4 on thebottom of the gyro case and out through four erecting ports l5, normallypartially closed by pendulous shutters IS, as well understood in theart.

The horizon bar 3 is shown as actuated in the usual manner both forpitch and roll from a pin l1 extending from the rotor casing through anarcuate slot 18 in the gimbal ring 8 and through a normally horizontalslot 19 in the rearwardly extending arm 20 which carries the horizon bar3 and which is pivoted at 2| on the rear of the gimbal ring.

There is also shown on the extension 14 a baffie ring or spoiler 22having downwardly extending baflie members or shutters 23 lying justbeyond and displaced slightly from the. cut-off edges of the pendulousshutters l6. Such spoilers act to limit or reduce the erecting forceexerted by the jets from ports l5 for tilts of more than a few degrees,as more fully explained in my aforesaid prior patent.

In order to quickly brake the gyroscope to bring it to rest at will, Ihave shown a brake ring 26 slidably mounted above the rotor l3 andhaving a friction face 21 engaging the rotor in its braking position.Said ring is shown as guided,

lifted, and prevented from rotating by means of pins 28' threadedtherein and extending upwardly through holes 29 in bosses extending uptoa wardly from the top of the rotor casing. At their The air then passesthrough the on the rotor,

tops, the pins are secured to a plate 30 carried by a metallicexpansible bellows 3| mounted on top of the rotor casing. The interiorof said bellows is connected, preferably through a capillary tube 32, toa point having a differential pressure as compared to the interior ofthe case I when the rotor is running, such as the atmosphere. As shown,the pipe 32 leads through a small bore coupling 33 to the channel l2within the casing, through which air at substantially atmosphericpressure flows to the spinning jets In other words, the interior of thebellows is connected in the air supply line to the spinning jet or jets,which is maintained at a pressure above that in the case regardless ofthe type of air pump employed. When there is no differential airpressure applied to the bellows, it is biased to its collapsed positionas shown in Fig. 2, in which position the brake ring is forced down, bythe spring walled bellows and by its own weight, against the rotor I3with sufficient pressure to quickly bring it to rest. When the bellowsis expanded, on the other hand, the brake ring is raised to bring itsupper surface adjacent or against the top' of the interior of the casingll. Therefore, when the air supply is shut off, the bellows will becollapsed, the brake applied, and the center of gravity lowered by thelowering of the brake ring. When, however, the

therefore expand somewhat until the air pressure within the same isreduced in proportion to the fall in air pressure in casing I, thusfirst releasing the brake promptly. At the same time a slow flow of airwill start into the bellows through the capillary tube 32 from thesuperior pressure, approaching that of the atmosphere, within thechannel I2. The result is that the ring 21 is further slowly andgradually lifted until it reaches its highest position, preferablyagainst the top of the casing.

By balancing the gyroscope so that it is in neutral equilibrium with-the ring in this lifted position, it will be evident that the gyroscopewill be decidedly pendulous with the ring in the lowered position. Byrestricting the connection 32 to the interior of 'the bellows, thelifting of the ring is made'slow so that the gyroscope remains somewhatpendulous until the speed of the rotor has reached its normal value, sothat during the starting up period the pendulosity of the casing assistsin rapid erection in case the gyro happens to be inclined somewhat atthe start.

By my invention, therefore, I provide a very simple means for bothpreventing damage to the gyroscope during acrobatics by stopping therotor, and also assuring that the gyroscope quickly reaches the truevertical when again placed in operating condition. Both of theseimportant results are secured by the simple expedient'of quicklystopping the rotor and renabove description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

Having described my invention, what I claim and desire to secure byLetters Patent is:

1. In an artificial horizon for aircraft, the combination withauniversally mounted rotor bearing Casing,-a spinning means and a rotorjournaled therein, a spring applied brake biased to engage the rotor andbrake the same, and means responsive to the supply of power to saidrotor spinning means for releasing the brake.

2. An artificial horizon as claimed in claim 1, in which said brake israised and lowered to disengage and engage the rotor, whereby the centerof gravity of the rotor casing is lowered when the brake is engaged.

3. In a neutrally mounted gyroscopic horizon having an erecting device,the combination with the neutrally mounted rotor casing and a rotor androtor spining means therein, of a vertically adjustable brake in saidcasing forbrakirig the rotor and lowering the center of gravity to makesaid casing pendulous when said rotor is not spinning, and meansresponsive to the supply of operating power to said spinning means forlifting said brake to release the same and maintain the rotor casing inneutral equilibrium only while the lous when said rotor is notspinning,and resildering the device pendulous when shut down for any purpose,such as during such time. as acroient means responsive to the supply ofoperating air pressure to said rotor casing for lifting said brake,whereby the casing is pendulous and will remain upright when the rotoris not spirming, and is mounted in neutral equilibrium when the rotor isspinning. I

5. In a gyro-vertical, the combination with an air spun rotor, a casingfor the same mounted for oscillation about horizontal axes, anexpansible container on said casing, a brake secured to an end wall ofsaid container to be moved thereby against or away from the rotor, apassage for leading air into the casing under a pressure different fromthat surrounding the casing to spin the rotor, and a connection betweenthe interior of said expansible container and said passage for causingsaid container to expand to release the brake as pressure is supplied tospin the rotor.

6. In an artificial horizon for aircraft, the combination with aneutrally mounted rotor bearing casing, a rotor spining means and arotor journaled therein, a brake on said casing for quickly stopping therotor, and means for applying the brake and automatically lowering thecenter of gravity of said rotor bearing casing.

7. An artificial horizon as claimed in claim 6, having power means foroperating said rotor spinning means and means brought into action by theshuting off of said power means for applying said brake and lowering thecenter of gravity of the rotor bearing casing.

LESLIE F. CARTER.

